Several methods have already been proposed for making such plates. Thus, U.S. Pat. No. 3,306,956 describes a process wherein a mold is lined with a creased foil preparatorily to the casting of a layer of transparent or translucent synthetic resin designed to form the body of a decorative plate or panel to be produced. Another technique, described in our German Pat. No. 2,511,895 published Sept. 8, 1977, utilizes a rigid core formed from webs or a honeycomb structure to which a pair of thermoplastic cover plates are bonded on opposite sides; these plates may be provided, on their exposed surfaces, with an embossed pattern.